Hi Z Friends,

this is my my first post on here and I’ve searched for this issue but haven’t come up with anything. My 04 Z is strictly track, I bought it this way. Caged with bolt ons. It came with a plastic generic oil catch can and it seems after every race my catch can is completely full, sometimes to the point that it’s spitting out of the breather. It’s a messy situation and was wondering if anyone know what could be causing this. One friend told me could be crankcase pressure? I’m not sure.

thanks!

 

Where do you race in mass?

Is the catch can vented or still attached to the plenum?

Crankcase pressure would be from the rings as you know, I would do a dry/wet compression test. I believe 185 psi is the target. I had one way down at 85 dry/115 wet once...

 

 

Dry is dry. Just compression test it.

Wet test is when you drip a little bit of oil onto the piston rings and do it again to see if the oil seals the ring gaps.

Also that hose is probably for the PVC boss that goes into your intake. You can delete it to help prevent crank case pressure or plug it back in. It's mostly for emissions. I'm running mine vented with my turbo kit. It's up to you.

 

 

Wet is to test the piston rings and cylander walls.

If you do a wet test and you gain compression over a dry, you are having pressure escape past your rings. Because the oil will seal those gaps increasing pressure.

If it's the same as a dry test or with in a couple psi your rings and cylinders are sealed properly and aren't letting pressure to enter your crank case.

Edit: also shows for valve seal and head gasket leaks but most the time it really shows if your cylander is worn or not sealing.

 

Say my seals, head gaskets, cylinders are all good.. then what do you think the culprit of an overfilling catch can would be?

thanks for the info by the way!

 

Could be a number of things, some Z owners literally chase that down for years. But it's not just to Nissan, it plagues all sorts of different cars. Many cars see this in boost. Some people find a solution, some never do.

I'd start with putting a small pod filter on the open hose behind the intake. Then do a leak down and see what we get before we explore the rabbit hole.

 

First thing I'd check before doing all the compression testing b.s. would be to check the pcv valve. Dude has this chepo c.c. vented, so he may have removed the pcv guts. That's typical for someone who might vent to the atmosphere.

 

I'd still comp test. Its always good to know the condition and health of your motor.

Its not THAT hard. Just annoying to pull the plugs and coil packs. But not that bad.

 

 

 

If the guts in the pcv are missing, it's wide open and the vacuum via intake is going to town. Crank case ventilation would have nothing to do with misfires.

 

 

Vacuum via intake is what positive crank case ventilation is all about. On the drivers side fresh air is drawn through a connection on the intake pipe then into the crank case, though the passenger side valve cover, then through the pcv valve and finally into the lower collector. The lower collector or intake plenum pulls this air in through the crank case via the intake pipe.

 

Makes sense now!

I also forgot to mention that the Z was turbo’d by the previous owner.. so it would make sense for them to have gutted the PCV. Obviously the catch can oil fills under load, so there’s no real way to test it until I have a track day. Ugh

I guess I’ll have to check that out and maybe run another compression test.

 

Just pull your pcv valve out and look. You'll be able to see right through it.

 

Alright so I checked my pcv, it still has its guts and it seems as if it’s opening and closing fine.

But it when I went to take a pic of a pipe coming off the intake that I plugged I found another one that is not plugged at all.. tell me what you think..